I. Field of the Invention
The present invention relates to an erosion-protecting device for protecting a solenoid type electromagnetic valve from erosion thereof; the solenoid type electromagnetic valve is provided with a plate-type armature that is connected to an end part of a valve body which opens and closes a liquid passage (a fuel passage in a case of a fuel injection device), as well as, a solenoid core power supply body that is provided with a solenoidal coil integrated with the solenoid core in a solenoid case that is filled with the liquid.
II. Description of the Related Art
A solenoid type electromagnetic configured such that a plate-type armature connected to an end part of a valve body which opens and closes a fuel passage and a solenoid core power supply body comprising a solenoidal coil integrated with the solenoid core in a solenoid case that is filled up with the fuel are provided, and an attracting side face of the solenoid core power supply body attracts an armature when current is conducted through the solenoidal coil, while the attraction force between the attracting side face of the solenoid core power supply body and the attracted side face of the armature is released when the current conducted through the coil is cut off, are often used for fuel injection devices of diesel engines.
FIG. 3 shows an example of the solenoid type electromagnetic valve device according to a conventional technology.
The solenoid type electromagnetic valve device as shown in FIG. 3 comprises a plate-type armature 6 that is directly connected to an end part of a control valve (not shown) for opening and closing a fuel passage (not shown), as well as a solenoid core power supply body 101 that is provided with a solenoid core 11 integrated with a solenoidal coil 3 and housed in a solenoid case 2 of a box shape filled up with the fuel oil.
In the solenoid core power supply body 101, the solenoidal coil 3 is configured so that the coil 3 is placed around a middle protrusion part of an E-shaped solenoid core 11, the middle protrusion part being formed between a pair of grooves 11a as shown in FIG. 2; because of the pair of grooves 11a, the E-shape of the solenoid core 11 is formed; the interstices between the solenoid core 11 and the solenoidal coil 3 are filled with an insulation resin material that can be solidified after being filled.
The solenoid core power supply body 101 is housed in a housing 1; the housing 1 is fastened to a valve case it via an intermediate piece is having a hollow space therein.
When the solenoidal coil 3 is conducted with current, there arises an attraction force between an attracting side face 15 of the solenoid core power supply body 101, namely the lower end surface thereof, and an attracted side face 6b of the armature 6. The attraction force makes the attracting side face 15 attract the attracted side face 6b in a direction toward the side face 15 against the counterforce due to a spring 8. In addition, the gap between the attracting side face 15 and the attracted side face 6b is approximately 0.1 mm.
In this way, the control valve (not shown) that is fixed to the armature 6 moves (toward in the Y-arrow direction in FIG. 1) and closes the fuel passage (not shown) so that the fuel in a control room (not shown) is pressurized.
In the next place, when the current conducted through the solenoidal coil 3 is cut off, the attraction force between the attracting side face 15 of the solenoid core power supply body 101 and the attracted side face 6b of the armature 6 is released so that the control valve (not shown) opens and the pressure in the fuel passage (not shown) is released.
As described above, when the solenoid core power supply body 101 is actuated, the gap between the attracting side face 15 and the attracted side face 6b varies within a range of the clearance level of 0.1 mm; and the armature is operated with high-speed responsivity; under such a condition, a pressure change from a positive pressure to a negative pressure and vice versa is repeated in the gap between the attracting side face 15 and the attracted side face 6b causing cavitation phenomena to occur in the gap.
JP2008-151082 discloses a solenoid type electromagnetic valve device comprising a plate-type armature connected to an end part of a valve body which opens and closes a fuel passage and a solenoid core power supply body comprising a solenoidal coil integrated with the solenoid core in a solenoid case that is filled up with the fuel.
In the device disclosed by the patent reference, as shown in FIG. 3, when the above-described control valve closes, the pressure increases in the small gap between the attracting side face 15 of the solenoid core power supply body 101 and the attracted side face 6b of the armature 6.
Because of this pressure increase, the control valve is kept under a locked condition for preventing the control valve from bouncing; hence, as soon as the control valve is lifted and opened, the pressure in the space in which the armature 6 is housed increases; further, the pressure in the above-described small gap rapidly decreases causing the fluid (liquid, or usually fuel in a case of fuel injection devices) in the housing space of the armature 6 to flow into the small gap. As a result, the surfaces facing the small gap space between the solenoid core power supply body 101 and the armature 6 are prone to be damaged from the cavitation erosion.
Partly because the magnetic core (the iron core) of the solenoid core power supply body 101 is fixed in the solenoid case 2 by filling magnetism-insulation resin material, the erosion damage caused in the event of the cavitation is prone to finally causing a difficulty that is the breaking of the solenoidal coil 3.
Further, according to the disclosure of JP2008-151082, a thin plate-type valve is installed on the backside of the armature having a plurality of passage holes; thus, the armature moves slowly and the high-speed responsivity cannot be expected.